Analyzing ranking and rating data from participatory on-farm trials

Abstract

Responses in participatory on-farm trials are often measured as ratings (scores on an ordered but arbitrary scale) or rankings (respondents are simply asked to order treatments). Usual analysis of variance and linear model based analyses are not appropriate for these data. Alternative analyses based on generalized linear models are described in this paper. These methods can be successfully used when trial designs are irregular—a common characteristic of participatory trials—and when covariates are measured on each plot or farm in order to identify genotype x environment interaction